HEC: Data of Potentially Habitable Worlds

Last Update: May 11, 2017

The database of potentially habitable worlds (also known as small planets in the habitable zone) of the Habitable Exoplanets Catalog (HEC) identifies objects of interest for follow-up observations and for statistical studies, including both confirmed and unconfirmed exoplanets. The database is updated with corrections and additions as new results are available. The HEC corrects or model many of the planetary properties combining different databases, so the numbers might not necessarily match those of a particular exoplanets database.

Potentially Habitable Exoplanets (Main Database)

These are potentially habitable exoplanets discovered by different ground or space observatories, some still unconfirmed. They are divided into a conservative sample (i.e. those more likely to be rocky and support surface liquid water) and an optimistic sample (i.e. those less likely to be rocky or support surface liquid water). Mass or radius for an iron, rocky, and water composition are given when not available for comparison purposes (Seager et al., 2007). Equilibrium temperatures are calculated assuming a 0.3 bond albedo. All planets are sorted by an Earth Similarity Index (ESI) based on how similar they are to Earth's stellar flux and size (either measured from mass or radius). This is a working list and data might be constantly revised.

Figure A-1. All planets in and near the habitable zone. Those less than 2.5 Earth radii are labeled. A mass-radius relation was used to illustrate RV planets.

Table A-1. Conservative sample of potentially habitable planets.

Table A-2. Optimistic sample of potentially habitable planets.

Potentially Habitable Exoplanets (NASA Kepler Objects of Interest)

These are exoplanets discovered by the NASA Kepler primary mission (Q1-Q17 DR 24 KOI Catalog). Those already confirmed are listed by their Kepler names.They are divided into a conservative sample (i.e. those more likely to be rocky and support surface liquid water) and an optimistic sample (i.e. those less likely to be rocky or support surface liquid water). Estimated masses for a pure iron, rocky, and water composition, respectively, are given for comparison purposes (Seager et al., 2007). All planets are sorted by an Earth Similarity Index (ESI) based on how similar they are to Earth's radius and stellar flux. Equilibrium temperatures are calculated assuming a 0.3 bond albedo. Values for some objects might be different from other published results since this list is based on a fully automated dispositioning process. Estimates for the distance from Earth are only approximate. This is a working list and data might be constantly revised.

Figure K-1. Kepler (Q1-Q17 DR 24) planets in and near the habitable zone. Those less than 2.5 Earth radii are labeled.

Potentially Habitable Exoplanets (NASA Kepler K2 Mission)

These are exoplanets discovered by the NASA Kepler K2 mission (K2 Catalog). Those already confirmed are listed by their K2 names.They are divided into a conservative sample (i.e. those more likely to be rocky and support surface liquid water) and an optimistic sample (i.e. those less likely to be rocky or support surface liquid water). Estimated masses for a pure iron, rocky, and water composition, respectively, are given for comparison purposes (Seager et al., 2007). All planets are sorted by an Earth Similarity Index (ESI) based on how similar they are to Earth's radius and stellar flux. Equilibrium temperatures are calculated assuming a 0.3 bond albedo. Estimates for stellar flux and distance from Earth are only approximate. This is a working list and data might be constantly revised.

Figure K2-1. Kepler (K2) planets in and near the habitable zone. Those less than 2.5 Earth radii are labeled.

Teq - Equilibrium temperature in kelvins (K) assuming a 0.3 bond albedo (Earth = 255 K). Actual surface temperatures are expected to be larger than the equilibrium temperature depending on the atmosphere of the planets, which are currently unknown (e.g. Earth mean global surface temperature is about 288 K or 15°C).

Period - Orbital period in days (Earth = 365 days).

Distance - Distance from Earth in light years (ly).

ESI - Earth Similarity Index, a measure of similarity to Earth that summarizes how similar are these planets to the stellar flux, mass, and radius of Earth (Earth = 1.0). Results are sorted by this number. Planets more similar to Earth are not necessarily more habitable, since the ESI does not consider all factors necessary for habitability.